Yet another pig flu virus infects people

Federal health officials say this one has made three people in Minnesota sick. Like the other unusual flu strains reported this year, this strain, called H1N2v, has only been found in people who had close contact with pigs at a state fair, the Centers for Disease Control and Prevention reported on Friday.

It’s becoming clear that pigs and people can pass influenza viruses back and forth. Health experts are watching the new strains closely because they can mutate and mix with one another to create even newer strains. The worry is the new strains will spread and cause flu pandemics, similar to the global outbreak of H1N1 swine flu virus in 2009.

So far, the three new variants identified this year -- H3n2v (the little v stands for “variant”), H1N1v and now H1N2v – don’t spread easily from person to person. Almost everyone infected has been close to pigs. One person has died from the new H3N2v virus, but everyone else has recovered. H1N2v was reported twice before in humans, in one person in 2007 in Michigan and in one person in Minnesota in 2011.

“This virus is different from the H3N2v virus that, as of today, is reported to have caused 296 human infections across 10 U.S. states since July 2012. These additional human infections underscore the fact that swine influenza viruses can spread to people after close contact with infected pigs, and support the importance of ongoing surveillance for both human and swine influenza viruses,” the CDC says in a statement on its website.

All three people who got sick in Minnesota with the new H1N2v virus have recovered but two had to be treated in the hospital. All three had close contact with a pig.

The new H1N2v virus appears to have already mixed with the H1N1 swine flu virus that caused the 2009 pandemic and that is now circulating as seasonal flu. CDC says the genetic sequence of the new virus shows it has a gene from the older H1N1 strain. Health experts are afraid that one of these new viruses will mutate or mix in a way that both makes it deadly and that gives it the ability to spread from person to person.

The good news is that the virus has at least one other gene that resembles circulating seasonal flu, meaning many people will have immune resistance to it, either from vaccination or from having had the flu.

These new variants of flu are very rare. “As of September 7, 2012, 335 cases of infection with variant influenza viruses have been reported in the United States since 2005. Of these 335 cases, 13 have been H1N1v viruses, 317 have been H3N2v viruses and 5 have been H1N2v viruses,” CDC says.

“With the exception of one death, the remaining 334 people infected with variant viruses recovered from their illness.”

The CDC estimates that anywhere between 3,000 to 49,000 people a year die from flu in the United States. A lot depends on the strains circulating. CDC recommends that everyone get vaccinated against influenza every year. The vaccine formula usually changes a little bit each year to match the most common flu strains, although this year's flu vaccine is not formulated to protect against the newly discovered pig flu viruses H1N1v, H1N2v or H3N2v.